• SPM-based Nanotechnology

    SPM-based Nanotechnology

    Two decades ago the family of surface modification and patterning methods was enhanced with SPM-based nanotechnology, mainly represented by STM and AFM nanolithography [1456, 1457]. Since that time, proximal probe nanolithography increasingly often appears in the focus of interest of semiconductor device developers and draws the attention of the rest of the scientific community. This particular interest is due to the fact that nowadays state-of-the-art SPM equipment allows for direct scripting on surfaces in very accurate and well-controllable manner. Thus, it tends to become a promising and competitive alternative or useful addition to the well-established methods of electron-beam lithography and wet chemical etching.

    The first experiments on surface modification by means of proximal-probe techniques are performed by Dagata et al. [1027, 1312]. The technique of local anodic oxidation (LAO), proposed in these works, now is an approved one for writing very small oxide patterns on both metallic and semiconductor surfaces. Research groups worldwide employ this technique for the fabrication of nanoelectronic devices, nanoelectromechanical systems, electro-optical structures, and templates for chemical and biological self-assembly. According to National Institute of Standards and Technology, this method is given its own unique code, 81.16.Pr, in the regularly updating American Institute of Physics PACS (Physics and Astronomy Classification Scheme) database.

    The phenomenon of anodic nano-oxidation has been proven to be of electrochemical nature. The simplified mechanism is as follows. The thin water film covering the surface under monitored and controlled ambient humidity of about 50% serves as an electrolyte between the sample (anode) and the tip (cathode). The negatively biased tip (though in the first STM-based work [1027] positive biasing is used) imposes an external electric field which dissociates water molecules into oxidizing species, presumably OH. The field further enhances the vertical drift of these species away from the tip towards the surface where they react with the underlying atoms to form a localized oxide beneath the tip. The field strength decays across the growing oxide film and the oxide growth process self terminates at/below the critical electric field of the order of 109 V/m [159]. The growth rate of oxide occurs to be strongly dependent on the bias applied to the tip [182]. The growing oxide expands in both up and down directions relative to surface of the sample, the depth being slightly more than the protrusion. 

    Nanotechnology of Silicon

    A detailed mechanism of local oxidation particularly for silicon is investigated in the papers of Gordon et al. [1467], Avouris et al. [1078, 1468], Dagata et al. [1474].

    The "dry" technique of local oxidation involves removing hydrogen atoms on an H-passivated silicon surface by means of an STM or AFM tip in vacuum. Depassivated areas can then be oxidized when exposed to an air environment due to the high reactivity of bare silicon [1456].

    Using contact mode AFM Lee et al. [1462] mechanically remove the passivating hydrogen layer by means of a silicon nitride cantilever applying forces of about several tens nN for subsequent oxidizing with ambient oxygen.

    Campbell et al. [182] suggest that using AFM with a conductive tip offers the advantage over STM in that the exposure and imaging mechanism are decoupled. This guarantees independent writing and subsequent imaging of the written pattern without fear of additional exposure.

    The ambient relative humidity (RH) affects drastically the aspect ratio of written patterns due to varying of the water film thickness on the surface of the specimen as shown in a paper of Avouris et al. [1468] who perform nanooxidation experiments within the range of 10 - 95% RH. It is revealed that the water film not only supplies the oxidizing species, but its finite conductance also leads to a defocusing of the electric field, which degrades the lateral resolution of the process. The highest aspect ratio structures form at about 14% RH though an optimal value from a different source is considered to be about 50% RH.

    By the opinion of Moon et al. [1489] control of the hydrophilicity would enlarge the applicability of LAO technique to practical applications where fabrication and patterning of thicker oxide are required. A significant difference is found for nanooxidation of silicon surfaces treated beforehand with hydrophilic (NH4OH : H2O2 : H2O = 1 : 1 : 10 known as SC1) and hydrophobic (HF : H2O = 1 : 100) solutions which apparently affect the parameters of the water layer on the oxidizing surface. It is found that the average height (width) of the oxide line is 4.8 nm (550 nm) for the former surface and 1.9 nm (340 nm) for the latter one for a bias voltage of 18 V and a scan rate of 2.3 µm/s. Thus, there is another way to control water layer parameters and, therefore, growing oxides besides ambient humidity.

    Nanoscale pits in silicon fabricated by anodic oxidation are considered as a possible nucleation sites in crystal growth and regions for metal embedding for quantum devices [1490].

    Besides SiO2, there is another widely used electronic material possessing higher dielectric constant. It is Si3N4 or SixNy due to its usual nonstoichiometry. Having in mind its usefulness as a material for nanolithography Pyle et al. [1469] and Workman et al. [227] study the growth of silicon nitride lines on the H-terminated silicon substrate in the atmosphere of NH3. It is shown that Faraday current also exist during growth pointing to the electrochemical nature of this process. That gives rise to deduction of a possible growth mechanism of nanolithographed nitride lines. Following this model, numerical evaluations reveal low efficiency of the process attributed to the presence of a tunneling current that could be diminished by an additional insulating layer on the tip apex. The authors believe that the value of the Faraday current probably can be used to control the growth rate.

    Nanotechnology of silicon, thus, continues attracting much attention and is worthy of separate brief description. By itself it can hardly be considered as sufficient for fabrication of a complete device. It should be rather recognized as an intermediate stage for the fabrication of more complicated nanostructures involving metal patterning, various etching techniques, etc. Possible applications of these oxide patterns are quantum and molecular devices, optical gratings, sites for immobilization of biological macromolecules and a many others.

    Nanotechnology of AIIIBV semiconductors

    Multilayer semiconductor heterostructures based on AIIIBV compounds represent a relatively novel class of objects in which the electrons are confined to a very thin, high mobility area, the so-called 2-dimensional electron gas (2DEG), underneath the surface, the depth being in order of several tens nanometers. Using these structures one can build devices, which rely on the discreteness of the electronic charge.

    For instance, single-electron transistors (SETs) defined in a two-dimensional electron gas of a semiconductor heterostructure known also as quantum dots (QDs) are of growing interest. Compared to the various other methods of fabrication of such devices AFM nanolithography provides many advantages, in particular small lateral depletion lengths and high specularity of the scattering at the boundaries [1472].

    A double-dot SET fabricated by Lüscher et al. [130] exhibits steep potential walls and a lateral depletion length of less than 20 nm, compared with the 100 nm value for an electron-beam lithography defined device. It is also shown, that operating the QDs with positive top gate voltages results in excellent transfer of the lithographic pattern into the electron gas.

    Oxide lines written on the surface of multilayer AIIIBV devices with delta-doped structure can serve as electrical barriers in the patterning of electronic devices. The main advantage of this technique over the more conventional and well-established split-gate technique is the strong lateral confinement provided by oxide lines, resulting in relatively high sub-band energy spacing. This way it is possible even to constrict a 2DEG at geterojunction interface into a narrow one-dimensional electron channel which exhibits quantized conductance at low temperatures as reported by Nemutudi et al. [159].

    Other experiments on modification of 2DEG are reported by Sasa et al. [191, 219] in application to GaSb/AlGaSb/InAs heterostructures. After nanooxidation samples are immersed in water in order to remove oxides. Authors showed feasibility of formation of periodical structures modulating 2DEG and noted that etching speed of oxidized GaSb and AlGaSb layers increases greatly if compared with non-oxidized ones.

    Fabrication of oxide wires on heavily doped p-type GaAs and n-type InGaP is investigated by Matsuzaki et. al [115]. A threshold bias voltage needed to produce the wires varies from 3 to 35 volts depending on the tip size. Dimensions of the wires are below 30 nm. Later, 10 nm size is reached using a special a-C tip formed on the apex of usual cantilever by electron beam deposition [107].

    Held et al. [1475] suggest that local anodic oxidation of high electron mobility transistors provides a novel method to define nanostructures and in-plane gates. Two examples, namely antidots and quantum point contacts as in-plane gate transistors are fabricated and their performance at liquid nitrogen temperatures is discussed.

    Nanotechnology of metals

    Beginning from the earliest works such as that of Sugimura et al. [1476], SPM-based nanotechnology is successfully applied for modifying metal surfaces as well: Ti [159, 181, 1037, 1459, 1461, 1493], Nb [1461, 1473, 1494, 1495, 1496, 1497], V [631], Cr [1492], Ni [1195], Al [1460, 1498] and Au [880, 1491].

    Vaccaro et al. [631] state that vanadium is a probable alternative to commonly used titanium since the oxidized line width is smaller and the height is higher for the former under the same conditions.

    Boisen et al. [1460] use aluminium and aluminium oxide written by AFM nanolithography as reactive ion etch (RIE) masks for simple fabrication of suspended submicron silicon and silicon oxide structures. Aluminium is a commonly used metal in complementary metal-oxide-semiconductor (CMOS) device fabrication. Furthermore, RIE is a widely used etch technique for CMOS processing whereas KOH is not suitable due to the consequent contamination by potassium ions. Hence, this patterning technique is CMOS compatible, making it in principle, possible to fabricate advanced nanomechanical structures with integrated microelectronics. Two years earlier E. S. Snow et al. [1498] manufacture atomic point contacts by using anodic oxidation of thin Al films. Quantized decrease in conductance of Al nanowires during final stages of anodization in discrete steps of ~2e2/h is observed.

    Several groups report fabrication non-AIIIBV quantum devices such as metal-oxide SETs mentioned above [1453, 1473, 1496, 1497] metal-insulator-metal junctions [181, 1495, 1493], tunneling barriers [1459, 1461].

    Shmidt et al. [1461] investigate another route for oxidizing thin metal Ti and Nb films with nanometer-scale resolution. The process called Current-Induced Local Oxidation (CILO) involves applying high in-plane current densities to very narrow metal strips (in order of 100 nm wide) embraced by oxide regions previously fabricated by means of standard AFM nanooxidation, which results in the formation of an insulating oxide barrier between these two regions in a self-limiting fashion. In this way a tunneling metal-oxide-metal junction appears. The authors note that the current-induced oxidation occurs under conditions entirely different from those in AFM tip-induced oxidation. In the latter case, the oxidation is forced by high electric fields of 107 V/cm oriented perpendicularly to the surface, which drive the oxidant into the film. In contrast, the stress voltage during the CILO process leads to electric fields of 105 V/cm, which are not only orders of magnitude lower but also oriented in the plane of the film. Towards the end of the barrier formation, only atomic-scale channels remain unoxidized. Despite a strongly increased current density, the oxidation rate decreases drastically and the conductance drops in steps of about 2e2/h. This gives evidence of ballistic transport and superior stability of such metallic nanowires against current-induced forces as compared with the bulk metal, which may be of great importance for future atomic-scale electronic devices.

    For soft metals a direct method of mechanical machining can be used which is considered separately in the following paragraph in respect to nonmetal materials.

    Modification of thin gold films can serve as an example. Schumacher et al. [880] explore contact AFM in constant force mode to create holes and grooves in thin Au films. When small forces in the order of nN are applied, displacement only of small grains takes place, and when applying µN forces it is possible to create deep groves down to the mica substrate. A set of cantilevers with spring constants between 0.05 and 25 N/m is used for these experiments.

    Nanotechnology of soft materials

    Modification of relatively soft materials can be performed using direct nanoscratching by means of a probe tip as partially described above for semiconductor heterostructures and Au coatings. Another way is to use electron sensitive organic compounds that can be modified under appropriate voltages applied by a conductive AFM or STM tip.

    Simple preparation of Langmuir-Blodgett (LB) films and Self-Assembled Monolayers (SAM) deposited on different substrates is the easiest way for nanoscale patterning that has many advantages over conventional electron beam lithography and photolithography. All above-mentioned materials can serve as substrates for subsequent development. Applicability of nanooxidation and local elecron-beam lithography to this systems depends upon a number of factors. For instance, the thickness of the covering organic layers must be small enough due to the limited penetration depth of low energy electrons emitted via STM or AFM probes. Their chemical composition should also be properly adjusted. For example, some terminal groups in organic SAMs may prevent oxidation and others may enhance it [259]; various metal cations may affect in a different way the anodization process for inorganic SAMs [1485]; various mixture ratios for preparation of LB films results in different anodization conditions [1471].

    Takano and Fujihira [290] investigate lithography of thin chromium films on a quartz plate covered with a LB film (21 monolayers thick) of omega-tricosenoic acid as a resist. The authors use mechanical nanoscratching for writing patterns with subsequent reactive ion etching of cromium film through the grooves defined. Normal forces as small as 0,5 nN is needed for removal of the resist.

    For aurum nanopatterning Haesendonck et al. [1482] utilize the same compound as an elecron sensitive resist. LB film consisted of mearly 4 monolayers and was 12 nm thick. It is known that omega-tricosenoic acid acts as a negative low-contrast resist when exposed with a high-energy electron beam. In this work exposure of such LB film is performed with the electron beam being emitted by an STM tip. After a detailed study of the influence of the exposure conditions on the quality of the fine-line patterns it is found that the optimum voltage for the exposure is close to 10 V. Lower voltages often cause incomplete exposure of the resist layer whereas higher voltages result in an undesirable increase of the minimum achievable line width. The authors claim that for an average quality tip linewidths of less than 50 nm could easily be achieved. In order to write the desired structures, a computer controlled pattern generator to obtain the x and y motion of the STM tip is designed. In contrast to the classical high-energy electron beam lithography, topographic images can also be obtained with the STM since the resist does not suffer exposure under voltages below 5 V. A similar approach is proposed in the paper of Wilder et al. [1499] where 30 nm wide features are formed in a 65-nm-thick resist by means of AFM conductive tip and then transferred through reactive ion etching into the silicon substrate.

    Lee et al. [259] use AFM nanooxidation to pattern the silicon surface through SAMs of different composition prepared on a negatively charged Si-wafer. The monolayer thickness does not exceeded 21 Å. It is found that results of nanopatterning under the same conditions depend upon the time of SAM formation and its chemical composition (namely, the nature of terminal groups). Complete coverage is achieved in adsorption time of 5 and 10 min with ideal film thickness of 17-18 Å. Oxide patterns written at relatively high rates of 0.36 mm/s and applied voltage of 20 V (corresponding current is 13 nA) is observed by subsequent AFM as 118 nm thick uniform lines 20 Å in height.

    Systematic discussion on the peculiarities of nanometer scale mechanical patterning of amorphous polymer surfaces with AFM tips in ambient conditions and in liquid cells is presented in the work of Pickering and Vancso [660]. A number of references can be found in this paper on surface modification of various oligomeric and polymeric systems. The authors undertake a critical review of contemporary data available for glassy polymers revealing the most common achievements as well as problems in this field.

    Nanotechnology of soft materials

         Modification of rather soft materials can be performed using direct nanoscratching technique by means of a cantilever tip as was partially described above for semiconductor heterostructures and Au coatings. Another way is to use electron sensitive organic compounds that can be modified under appropriate voltages applied by conducting AFM or STM tip.

         Rather simple preparation of Langmuir-Blodgett (LB) films and Self-Assembled Monolayers (SAM) deposited on different substrates is the easiest way for nanoscale patterning that takes many advantages over conventional electron beam lithography and photolithography. All above-mentioned materials can serve as substrates for subsequent development. Applicability of nanooxidation and local elecron-beam lithography to this systems depends upon a number of factors. For instance, thickness of the covering organic layers must be small enough due to limited penetration depth of low energy electrons emitted via STM or AFM probes. Their chemical composition also should be properly adjusted. For example, some terminal groups in organic SAMs may prevent oxidation and others enhance it [259]; various metal cations may affect different way on the anodization process for inorganic SAMs [1485]; various mixture ratios for preparation of LB films results in different anodization conditions [1471].

         Takano and Fujihira [290] investigated lithography of thin chromium films on a quartz plate covered with LB film (21 monolayers thick) of omega-tricosenoic acid as a resist. The authors used mechanical nanoscratching technique for writing needed patterns with subsequent reactive ion etching of cromium film through the grooves defined. Normal forces as small as 0,5 nN was needed for removal of the resist.

         For aurum nanopatterning Haesendonck et al. [1482] utilized the same compound as an elecron sensitive resist. LB film consisted of mearly 4 monolayers and was 12 nm thick. It is known that omega-tricosenoic acid act as a negative low-contrast resist when exposed with a high-energy electron beam. In this work exposure of such LB film was performed with the electron beam being emitted by an STM tip. After a detailed study of the influence of the exposure conditions on the quality of the fine-line patterns it has been found that the optimum voltage for the exposure is close to 10 V. Lower voltages often cause an incomplete exposure of the resist layer whereas higher voltages give rise to an undesirable increase of the minimum achievable line width. Authors claim that for an average tip quality the linewidths of less than 50 nm could always be achieved. In order to write the desired structures, a computer controlled pattern generator to obtain the x and y motion of the STM tip has been designed. In contrast to the classical high-energy electron beam lithography, one can also obtain topographic images with the STM since resist does not suffer exposure under voltages below 5 V. A similar approach was declared in the paper of Wilder et al. [1499] where 30 nm wide features was formed in 65-nm-thick resist by means of AFM conducting tip and then transferred through reactive ion etching into the silicon substrate.

         Lee et al. [259] used AFM nanooxidation technique to pattern silicon surface through SAMs of different composition prepared on the negatively charged Si-wafer. Monolayer thickness does not exceeded 21Å. It was found that results of nanopatterning under the same conditions depend upon the time of SAM formation and its chemical composition (namely, the nature of terminal groups). The complete coverage was achieved in adsorption time of 5 and 10 min with ideal film thickness of 17-18Å. Oxide patterns written at relatively high rates of 0,36 mm/s and applied voltage of 20 V (corresponding current was 13 nA) was observed by subsequent AFM as 118 nm thick uniform lines of 20Å in height.

         Systematic discussion on the peculiarities of nanometer scale mechanical patterning of amorphous polymer surfaces with AFM tips in ambient conditions and in liquid cell is presented in the work of Pickering and Vancso [660]. A number of references could be found in this paper on surface modification of various oligomeric and polymeric systems. The authors undertook a critical review of contemporary data available for glassy polymers revealing the most common regularities as well as problems in this field.

    Concluding remarks

         Common obstacles to be overcome in all nanolithography experiments as well as on the way to commercialization are wearing of SPM tip during the process and slow rates of writing.

         H. Dai at al. [1619] believe that the remedy is in use of nanotube probes possessing extraordinary mechanical and electric characteristics. Extremely thin patterns of several nanometer wide can be written by such probes without noticeable wearing. As authors claime, slow rates of writing (0,1 mm/s in 1996 [1463]) could be increased fivefold using nanotubes as compared with conventional tips and amount to 0,5 mm/s. A year later Snow and Campbell [1470] declare successful experiments on oxidation and metal silicide processes at speeds approaching to 10 cm/s (see also related paper [1454]).

         All investigations from above cited references concerning oxidation of AIIIBV compounds were performed in Tapping Mode nanooxidation AFM. Self-limiting nature of this process does not allow for high scanning rates, which often does not exceed 100-200 nm/s. At the same time, there is a number of works devoted to manufacturing of heterostructure-based devices by contact mode AFM or nanoscratching that make higher scan rate possible. Schumacher et al. [192] report fabrication of SET by this technique applying contact forces within 50-100 mN at a scan velocity of 100 µm/s, i.e. 2-3 orders of magnitude faster as compared with nanooxidation. The machining process is performed pressing the usual silicon non-contact AFM tip against the surface while multiply scanning along a line over the preformed Hall structure. After about 100 scan lines a local removal of the surface layers was achieved that is comparable to a shallow etch process.

         Prospects in using SAMs and LB films for patterning are quite promising provided that the problems of layers uniformity, chemical stability and absence of nanoscopic defects such as pinholes are successfully solved. In contrast to LB films, SAMs require the proper functional groups for chemisorption to the substrate and proper chemical structure in order to be sufficiently affected under relatively weak electron beams emitted by STM or AFM tips.

         Advances in nanooxidation allowed for demonstrating a possibility for fabrication of an extradense data storage media having fantastic capacity of 1,6 Tbit per square inch [1464]. Bits pattern on atomically flat titanium surface was written in the form of an array of regularly arranged oxide cones of about 1 nm in height and 6-8 nm in width. To produce such a fine structure with the pitch between individual bits as small as 20 nm, single-walled nanotube tips with 2-5 nm diameters were used. Similar array was fabricated by conventional cantilever three years earlier [1463] with the following parameters: width - 30 nm, height - 1 nm, pitch - 100 nm. This outmost achievement though will hardly be developed even into prototype device due to a number of technical issues to be addressed but thereby was demonstrated a necessity to apply further efforts to approach the commercialization of nanolithography in less exotic applications.

    An idea of parallelizm in respect to SPM-based nanotechnology is declared elsewhere (see, for example [1499]) and have to be implemented in viable commercial prototype as always has been demonstrated in application of AFM to data storage.

    Successful fabrication of various nanodevices, steady improvement of accuracy and feasibility of SPM apparatus and scanning control techniques envisage further development of SPM-based nanotechnology.

    Please, send all comments and suggestions concerning these pages to info@mikromasch.com

    ID Reference list (newly come references are marked red)
    1485 A study of positive charge effect on AFM anodization lithography using metal phosphate monolayers
    S. M. Kim, S. J. Ahn, H. Lee, E. R. Kim and H. Lee
    Ultramicroscopy, 91 (2002), 1-4, pp. 165-169
    219 AFM fabrication and characterization of InAs/AlGaSb nanostructures
    S. Sasa, T. Ikeda, A. Kajiuchi, M. Inoue
    Solid-State Electronics, 42 (1998), 7-8, 1069-1073
    181 AFM fabrication of metal-oxide devices with in situ control of electrical properties
    E.S. Snow, P.M. Campbell
    Physica B: Condensed Matter, 227 (1996), 1-4, 279-281
    290 AFM microlithography of a thin chromium film covered with a thin resist Langmuir-Blodgett (LB) film
    H. Takano, M. Fujihira
    Thin Solid Films, 273 (1996), 1-2, 312-316
    1471 AFM nanolithography on a mixed LB film of hexadecylamine and palmitic acid
    Sang Jung Ahn, Yun Kyeong Jang, Seung Ae Kim, Haeseong Lee and Haiwon Lee
    Ultramicroscopy, 91 (2002), 1-4, pp. 171-176
    1468 AFM tip induced and current induced local oxidation of silicon and metals
    Ph. Avouris, R. Martel, T. Hertel, and R.L. Sandström
    Applied Physics A, Mater. Sci. Process. 66 (1998), suppl., pt.1-2, p. S659
    155 AFM-based fabrication of lateral single-electron tunneling structures for elevated temperature operation
    L. Montelius, T. Junno, S.-B. Carlsson, L. Samuelson
    Microelectronic Engineering, 35 (1997), 1-4, 281-284
    182 AFM-based fabrication of Si nanostructures
    P.M. Campbell, E.S. Snow, P.J. McMarr
    Physica B: Condensed Matter, 227 (1996), 1-4, 315-317
    188 Anomalous current-voltage characteristics along the c-axis in YBaCuO thin films prepared by MOCVD and AFM lithography
    S. Yamamoto, A. Kawaguchi, S. Oda
    Physica C: Superconductivity and its Applications, 293 (1997), 1-4, 244-248
    1493 Application of STM Nanometer-Size Oxidation Process to Planar-Type MIM Diode
    K. Matsumoto, S. Takahashi, M. Ishii, M. Hoshi, A. Kurokawa, S. Ichimura, A. Ando
    Jpn. J. Appl. Phys., 34 (1995) pp. 1387-1390
    1078 Atomic force microscope tip-induced local oxidation of silicon: kinetics, mechanism, and nanofabrication
    Ph. Avouris, T. Hertel, and R. Martel
    Appl. Phys. Lett. 71 (1997), 2, 285-287
    1199 Chemically Well-Defined Lithography Using Self-Assembled Monolayers and Scanning Tuneling Microscopy in Nonpolar Organothiol Solutions
    C.B. Gorman, R.L. Carroll, Y. He, F. Tian and R. Fuierer
    Langmuir 16 (2000), 6312-6316
    1483 Controllable Nano-pit Formation on Si Surface with Scanning Tunneling Microscope
    N. Ueda, K. Sudoh, N. Li, T. Yoshinobu and H. Iwasaki
    Jpn. J. Appl. Phys., 38 (1999) pp. 5236-5238
    192 Controlled mechanical AFM machining of two-dimensional electron systems: fabrication of a single-electron transistor
    H.W. Schumacher, U.F. Keyser, U. Zeitler, R.J. Haug, K. Eberl
    Physica E: Low-dimensional Systems and Nanostructures, 6 (2000), 1-4, 860-863
    227 Current-dependent growth of silicon nitride lines using a conducting tip AFM
    R.K. Workman, C.A. Peterson, D. Sarid
    Surface Science, 423 (1999), 2-3, L277-L279
    1461 Current-induced local oxidation of metal films: Mechanism and quantum-size effects
    T. Schmidt, R. Martel, R. L. Sandstrom, and Ph. Avouris
    Appl. Phys. Lett. 73 (1998), 15, 2173-2175
    1020 Electrochemical nanolithography using scanning probe microscopy: Fabrication of patterned metal structures on silicon substrates
    H. Sugimura, N. Nakagiri
    Thin Solid Films, 281-282 (1996), 1-2, 572-575
    1193 Electron Beam and Scanning Probe Lithography: A Comparison
    K. Wilder, C.F. Quate, B. Singh, and D.F. Kyser
    J. Vac. Sci. Technol. B 16 (1998), 3864-3873
    1489 Enhanced Nano-oxidation on a SC1-treated Si Surface Using Atomic Force Microscopy
    W. C. Moon, T. Yoshinobu and H. Iwasaki
    Jpn. J. Appl. Phys., 41 (2002), pp.4754-4757
    1484 Experimental Measurement of the Intensity Profiles of a Low-Energy Electron Beam Extracted from a Scanning Tunneling Microscope Tip by Field Emission
    I. Kawamoto, N. Li, T. Yoshinobu and H. Iwasaki
    Jpn. J. Appl. Phys., 38 (1999) pp.6172-6173
    1619 Exploiting the properties of carbon nanotubes for nanolithography.
    H. Dai, N. Franklin, and J. Han
    Appl. Phys. Lett. 73 (1998), 1508-1510
    1472 Fabricating tunable semiconductor devices with an atomic force microscope
    R. Held, S. Lüscher, T. Heinzel, K. Ensslin, and W. Wegscheider
    Appl. Phys. Lett. 75 (1999), 1134-1136
    1198 Fabrication of Nanometer-Sized Protein Patterns using Atomic Force Microscopy and Selective Immobilization
    K. Wadu-Mesthrige, N.A. Amro, J.C. Garno, S. Xu, and G.-Y. Liu
    Biophysical Journal 80 (2001), 1891-1899
    1490 Fabrication of Nanopit Arrays on Si(111)
    W. C. Moon, T. Yoshinobu and H. Iwasaki
    Jpn. J. Appl. Phys., 38 (1999), pp. 483-486
    1196 Fabrication of Semiconductor Nanostructures by Nanoindentation of Photoresist Layers Using Atomic Force Microscopy
    K. Wiesauer and G. Springholz
    J. Appl. Phys. 88 (2000), 7289-7297
    1197 Fabrication of Silicon and Metal Nanowires and Dots Using Mechanical Atomic Force Lithography
    S. Hu, A. Hamidi, S. Altmeyer, T. Koster, B. Spangenberg, and H. Kurz
    J. Vac. Sci. Technol. B16 (1998), 2822-2824
    1460 Fabrication of submicron suspended structures by laser and atomic force microscopy lithography on aluminum combined with reactive ion etching
    A. Boisen, K. Birkelund, O. Hansen, and F. Grey
    J. Vac. Sci. Technol. B16 (1998), 6, 2977-2981
    1459 Fabrication of Ti/TiOx tunneling barriers by tapping mode atomic force microscopy induced local oxidation
    B. Irmer, M. Kehrle, H. Lorenz, and J. P. Kotthaus
    Appl. Phys. Lett. Vol. 71 (1997), 12, 1733-1735
    1486 Formation of Nano-pyramids of Layered Materials with AFM
    S. Antoranz Contera, T. Yoshinobu, H. Iwasaki, Z. Bastl and P. Lostak
    Ultramicroscopy, 82 (2000) pp.165-170.
    1469 Growth of silicon nitride by scanned probe lithography
    J.L. Pyle, T.G. Ruskell, R.K. Workman, X. Yao, D. Sarid
    J. Vac. Sci. Technol. B15 (1997), 1, 38-39
    1454 High speed patterning of a metal silicide using scanned probe lithography
    E. S. Snow, P. M. Campbell, and F. K. Perkins
    Appl. Phys. Lett. 75 (1999), 1476-1478
    107 Improvement of nanoscale patterning of heavily doped p-type GaAs by atomic force microscope (AFM)-based surface oxidation process
    Y. Matsuzaki, A. Yamada, M. Konagai
    Journal of Crystal Growth, 209 (2000), 2-3, 509-512
    191 InAs/AlGaSb nanoscale device fabrication using AFM oxidation process
    S. Sasa, T. Ikeda, C. Dohno, M. Inoue
    Physica E: Low-dimensional Systems and Nanostructures, 2 (1998), 1-4, 858-861
    130 In-plane Gate Single Electron Transistor Fabricated by AFM Lithography
    S. Lüscher, A. Fuhrer, R. Held, T. Heinzel, K. Ensslin, W. Wegscheider, M. Bichler
    Journal of Low Temperature Physics, 118 (2000), 5/6, 333-342
    1475 In-plane gates and nanostructures fabricated by direct oxidation of semiconductor heterostructures with an atomic force microscope
    R. Held, T. Vancura, T. Heinzel, K. Ensslin, M. Holland, and W. Wegscheider
    Appl. Phys. Lett. 73 (1998), 262-264
    1487 Lift-off Patterning of Thin Au Films on Si Surfaces with Atomic Force Microscope
    W. C. Moon, T. Yoshinobu and H. Iwasaki
    Ultramicroscopy, 82 (2000), pp.119-123
    1477 Low Energy Electron Beam Stimulated Surface Reaction: Selective Etching of SiO2/Si Using Scanning Tunneling Microscope
    N. Li, T. Yoshinobu and H. Iwasaki
    Jpn. J. Appl. Phys., 37 (1998), pp.L995-L998
    1478 Low Energy Electron Stimulated Etching of Thin Si Oxide Layer Using STM
    N. Li, T. Yoshinobu and H. Iwasaki
    J. Vac. Soc. Jpn., 42 (1999), p.488
    1481 Low-energy Electron Stimulated Etching of Thin Si-oxide Layer in Nanometer Scale Using Scanning Tunneling Microscope
    N. Li, T. Yoshinobu and H. Iwasaki
    Jpn. J. Appl. Phys., 38 (1999), pp.L252-L254
    1194 Making Gold Nanostructures using Self-Assembled Monolayers and a Scanning Tunneling Microscope
    E. Delamarche, A.C.F. Hoole, B. Michel, S. Wilkes, M. Despont, M.E. Welland, and H. Biebuyck
    J. Phys. Chem. B 101 (1997), 9263-9269.
    1467 Mechanisms of surface anodization produced by scanning probe microscopes
    A. E. Gordon, R. T. Fayfield, D. D. Litfin, and T. K. Higman
    Journal Vac. Sci. Tech. B13 (1995), 6, 2805-2808
    1195 Metal Pattern Fabrication Using the Local Electric Field of a Conducting Atomic Force Microscope Probe
    S.L. Brandow, J.M. Calvert, E.S. Snow, and P.M. Campbell
    J. Vac. Sci. Technol. A15 (1997), 1455-1459
    159 Modification of a shallow 2DEG by AFM lithography
    R. Nemutudi, N.J. Curson, N.J. Appleyard, D.A. Ritchie, G.A.C. Jones
    Microelectronic Engineering, 57-58 (2001), 967-973
    1027 Modification of hydrogen-passivated silicon by a scanning tunneling microscope in air
    J. A. Dagata, J. Schneir, H. H. Harary, C. J. Evans, M. T. Postek and J. Bennett
    Appl. Phys. Lett. 56 (1990), 2001
    880 Modification of thin gold films with a scanning force microscope
    H.W. Schumacher, B. Kracke, B. Damaschke
    Thin Solid Films, 264 (1995), 2, 268-272
    115 Nanofabrication of heavily doped p-type GaAs and n-type InGaP by atomic force microscope (AFM)-based surface oxidation process
    Y. Matsuzaki, K.-I. Yuasa, J.-I. Shirakashi, E. Chilla, A. Yamada, M. Konagai
    Journal of Crystal Growth, 201-202 (1999), 656-659
    1492 Nanofabrication of thin chromium film deposited on Si(100) surfaces by tip induced anodization in atomic force microscopy
    D. Wang, L. Tsau, K. L. Wang, and P. Chow
    Appl. Phys. Lett. 67 (1995), pp. 1295-1297
    1476 Nanofabrication of Titanium Surface by Tip-Induced Anodization in Scanning Tunneling Microscopy
    H. Sugimura,T. Uchida, N. Kitamura and H. Masuhara
    Jpn. J. Appl. Phys., 32 (1993), 4A, p. L553-L555
    1479 Nano-fabrication on Si oxide/Si Surface by Using STM: a Low Energy Electron Beam Stimulated Reaction
    N. Li, T. Yoshinobu and H. Iwasaki
    Applied Surfice Science, 141 (1999), pp.305-312
    1480 Nano-fabrication on SiO2/Si with Scanning Tunneling Microscope: Mechanism of the Low-energy Electron-stimulated Reaction
    N. Li, T. Yoshinobu and H. Iwasaki
    Appl. Phys. Lett. 74 (1999) pp.1621-1623
    1457 Nanofabrication with Proximal Probes
    E.S. Snow. P.M. Campbell, and F.K. Perkins
    IEEE Proc. 85 (1997), 601
    1036 Nanolithography on hydrogen-terminated silicon by scanning-probe microscopy
    C. Schonenberger, N. Kramer
    Microelectronic Engineering, 32 (1996), 1-4, 203-217
    1463 Nanometer scale lithography of silicon(100) surfaces using tapping mode atomic force microscopy
    J. Servat, P. Gorostiza, F. Sanz, F. Pérez-Murano, N. Barniol, G. Abadal, and X. Aymerich
    J. Vac. Sci. Technol. A14 (1996), 3, 1208-1212
    1037 Nanometer scale lithography on silicon, titanium and PMMA resist using scanning probe microscopy
    E. Dubois, J.-L. Bubbendorff
    Solid-State Electronics, 43 (1999), 6, 1085-1089
    1462 Nanometer-scale lithography on H-passivated Si(100) by atomic force microscope in air
    H. T. Lee, J. S. Oh, S.-J. Park, K.-H. Park, J. S. Ha, H. J. Yoo, J.-Y. Koo
    J. Vac. Sci. Technol. A15 (1997), 3, 1451-1454
    631 Nano-oxidation of Vanadium Thin Films using Atomic Force Microscopy
    P. O. Vaccaro, S. Sakata, S. Yamaoka, I. Umezu, A. Sugimura
    Journal of Materials Science Letters, 17 (1998), 22, 1941-1943
    259 Nanopatterning of self-assembled monolayers on Si-surfaces with AFM lithography
    W.B. Lee, Y. Oh, E.R. Kim, H. Lee
    Synthetic Metals, 117 (2001), 1-3, 305-306
    1491 Nanoscale Patterning of Au Films on Si Surfaces by Atomic Force Microscopy
    W. C. Moon, T. Yoshinobu and H. Iwasaki
    Jpn. J. Appl. Phys., 38 (1999), pp. 6952-6954
    1482 Nanowire bonding with the scanning tunneling microscope
    C. Van Haesendonck, L. Stockman, R. J. M. Vullers, Y. Bruynseraede, L. Langer, V. Bayot, E. Grivei, J.-P. Issi, J.P. Heremans, C.H. Olk
    Surface Science 386 (1997), 279-289
    1495 Nb/Nb Oxide-Based Planar-Type Metal/Insulator/Metal (MIM) Diodes Fabricated by Atomic Force Microscope (AFM) Nano-Oxidation Process
    J. Shirakashi, M. Ishii, K. Matsumoto, N. Miura and M. Konagai
    Jpn. J. Appl. Phys., 36 (1997), p. L1120
    1499 Noncontact Nanolithography Using the Atomic Force Microscope
    K. Wilder, C.F. Quate, D. Adderton, R. Bernstein, and V. Elings
    Appl. Phys. Lett. 73 (1998), 2527-2529
    660 On the formation of oriented nanometer scale patterns on amorphous polymer surfaces studied by atomic force microscopy
    J.P. Pickering, G.J. Vancso
    Applied Surface Science, 148 (1999), 3-4, 147-154
    1497 Room Temperature Nb-Based Single-Electron Transistors
    J. Shirakashi, M. Ishii, K. Matsumoto, N. Miura and M. Konagai
    Jpn. J. Appl. Phys., 37 (1998), p. 1594
    1453 Room temperature operated single electron transistor made by a scanning tunnelling microscopy/atomic force microscopy nano-oxidation process
    K. Matsumoto
    International Journal of Electronics 86 (1999), 641-662
    1488 Scanning Tunneling Microscopy Nanofabrication of Electronic Industry Compatible Thermal Si Oxide
    N. Li, T. Yoshinobu and H. Iwasaki
    Ultramicroscopy, 82 (2000), pp.97-101
    1312 Selective-area epitaxial growth of gallium arsenide on silicon substrates patterned using a scanning tunneling microscope operating in air
    J.A. Dagata, W. Tseng, J. Bennet, C.J. Evans, J. Schneir, H.H. Harary
    Appl. Phys. Lett. 57 (1990), 23, 2437
    36 Si nanofabrication using AFM field enhanced oxidation and anisotropic wet chemical etching
    K. Morimoto, K. Araki, K. Yamashita, K. Morita, M. Niwa
    Applied Surface Science, 117-118 (1997), 652-659
    1465 Silicon nanowires with sub 10 nm lateral dimensions: From atomic force microscope lithography based fabrication to electrical measurements
    B. Legrand, D. Deresmes, and D. Stiévenard
    J. Vac. Sci. Tech. B20 (2002), 862
    1498 Single-atom point contact devices fabricated with an atomic force microscope
    E. S. Snow, D. Park, and P. M. Campbell
    Appl. Phys. Lett. 69 (1996), pp. 269-271
    1473 Single-electron charging effects in Nb/Nb oxide-based single-electron transistors at room temperature
    J. Shirakashi, K. Matsumoto, N. Miura, and M. Konagai
    Appl. Phys. Lett. 72 (1998), 1893-1895
    1496 Single-Electron Transistors (SETs) with Nb/Nb Oxide System Fabricated by Atomic Force Microscope (AFM) Nano-Oxidation Process
    J. Shirakashi, M. Ishii, K. Matsumoto, N. Miura and M. Konagai
    Jpn. J. Appl. Phys., 36 (1997), p. L1257
    1482 STM Nano Fabrication Process Using SiO2 Film (in Japanese)
    H. Iwasaki, N. Li, and T. Yoshinobu
    Journal of the Surface Science Society of Japan, 20 (1999), pp.49-56
    1458 STM/AFM Nano-Oxidation Process to Room-Temperature-Operated Single-Electron Transistor and Other Devices
    K. Matsumoto
    IEEE Proc. 85 (1997), 612
    220 Structuring of mica surfaces with a vibrating AFM tip
    J. Kuppers, T. Schimmel, R. Kladny, V. Popp
    Surface Science, 401 (1998), 1, 105-111
    1466 Sub-50 nm nanopatterning of metallic layers by green pulsed laser combined with atomic force microscopy
    S. M. Huang, M. H. Hong, B. S. Luk
    J. Vac. Sci. Tech. B20 (2002), 1118
    1494 Surface Modification of Niobium (Nb) by Atomic Force Microscope (AFM) Nano-Oxidation Process
    J. Shirakashi, M. Ishii, K. Matsumoto, N. Miura and M. Konagai
    Jpn. J. Appl. Phys., 35 (1996), p. L1524
    1464 Terabit-per-square-inch data storage with the atomic force microscope
    E. B. Cooper, S. R. Manalis, H. Fang, H. Dai, K. Matsumoto, S. C. Minne, T. Hunt, and C. F. Quate
    Appl. Phys. Lett. 75 (1999), 22, 3566-3568
    190 Terahertz excitation of AFM-defined room temperature quantum dots
    N. Qureshi, M. Reddy, J.S. Scott, T. Noda, Y. Nakamura, I. Tanaka, H. Sakaki, S.J. Allen, M.J.W. Rodwell, I. Kamiya
    Physica E: Low-dimensional Systems and Nanostructures, 2 (1998), 1-4, 701-703
    1470 The Technique and Mechanism of Scanned Probe Oxidation
    E.S. Snow and P.M. Campbell
    Seventh Foresight Conference on Molecular Nanotechnology, October 15-17, 1999, Santa Clara, CA
    1456 UHV STM Nanofabrication: Progress, Technology Spin-Offs, and Challenges
    J.W. Lyding
    IEEE Proc. 85 (1997), 589
    1474 Understanding scanned probe oxidation of silicon
    J. A. Dagata, T. Inoue, J. Itoh, and H. Yokoyama
    Appl. Phys. Lett. 73 (1998), 271-273
    1203 Vertical Manipulation of Individual Atoms by a Direct STM Tip-Surface Contact on Ge(111)
    G. Dujardin, A. Mayne, O. Robert, F. Rose, C. Joachim, and H. Tang
    Phys. Rev. Lett. 80 (1998) 3085
    1249 Manipulation of nanoscale components with the AFM: principles and applications
    A. A. G. Requicha, S. Meltzer, F. P. Teran Arce, J. H. Makaliwe, H. Siken, S. Hsieh, D. Lewis, B. E. Koel and M. Thompson
    IEEE Int'l Conf. on Nanotechnology, Maui, HI, October 28-30, 2001.
    1253 Imaging and manipulation of gold nanorods with an Atomic Force Microscope
    S. Hsieh, S. Meltzer, C. R. C. Wang, , A. A. G. Requicha, M. E. Thompson and B. E. Koel
    J. Physical Chemistry B, 106 (2002), 2, pp. 231-234
    1254 Manipulation of gold nanoparticles in liquid environments using scanning force microscopy
    R.Resch, D. Lewis, S. Meltzer, N. Montoya, B.E. Koel, A. Madhukar, A.A.G. Requicha and P. Will
    Ultramicroscopy, 82 (2000), pp. 135-139
    1256 Linking and manipulation of gold multi-nanoparticle structures using dithiols and scanning force microscopy
    R. Resch, C. Baur, A. Bugacov, B.E. Koel, P.M. Echternach, A.Madhukar, N. Montoya, A.A.G. Requicha, Peter Will
    J. Physical Chemistry B, 103 (1999), pp. 3647-3650
    1257 Building and manipulating 3-D and linked 2-D structures of nanoparticles using scanning force microscopy
    R. Resch, C. Baur, A. Bugacov, B. E. Koel, A. Madhukar, A. A. G. Requicha and P. Will
    Langmuir 14 (1998), 23, pp. 6613-6616
    1258 Nanoparticle manipulation by mechanical pushing: underlying phenomena and real-time monitoring
    C. Baur, A. Bugacov, B. E. Koel, A. Madhukar, N. Montoya, T. R. Ramachandran, A. A. G. Requicha, R. Resch and P. Will
    Nanotechnology 9 (1998), 4, pp. 360- 364
    1259 Manipulation of nanoparticles using dynamic force microscopy: simulation and experiments
    R. Resch, C. Baur, A. Bugacov, B. E. Koel, A. Madhukar, A. A. G. Requicha and P. Will
    Applied Physics A: Materials Science & Processing, 67 (1998), 3, pp. 265-271
    1260 Direct and Controlled Manipulation of Nanometer-Sized Particles Using the Non-Contact Atomic Force Microscope
    T. R. Ramachandran, C. Baur, A. Bugacov, A. Madhukar, B. E. Koel, A. Requicha, and C. Gazen
    Nanotechnology 9 (1998), 3, pp. 237-245
    1699 Fabrication of nanodevices using AFM nanolithography and manipulations
    Richard Martel
    The 200th Meeting of The Electrochemical Society, Inc. and the 52nd Meeting of The International Society of Electrochemistry, San Francisco, California, September 2-7, (2001), 518
    2588 Lithography by tapping-mode atomic force microscopy with electrostatic force modulation
    B.I. Kim, U.H. Pi, Z.G. Khim, S. Yoon
    Applied Physics A: Materials Science & Processing, 66 (1998) 7, S95-S98
    2577 Direct-Writing of Polymer Nanostructures: Poly(thiophene) Nanowires on Semiconducting and Insulating Surfaces
    Maynor B. W., Filocamo S. F., Grinstaff M. W., Liu J.
    J. Am. Chem. Soc. (Communications), 124 (2002) 4, 522-523
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